Oxidation States of Graphene: Insights from Computational Spectroscopy

TL;DR

This paper uses first principles computational spectroscopy to interpret XPS data of graphene oxide, proposing new oxidation species and advancing understanding of its complex structure.

Contribution

It introduces a first principles approach to interpret XPS data of GO and proposes a new structural model with novel oxidation species.

Findings

Calculated binding energies match experimental XPS data

Proposed new oxidation species: epoxy pair and epoxy-hydroxy pair

Demonstrated the effectiveness of computational spectroscopy in GO analysis

Abstract

When it is oxidized, graphite can be easily exfoliated forming graphene oxide (GO). GO is a critical intermediate for massive production of graphene, and it is also an important material with various application potentials. With many different oxidation species randomly distributed on the basal plane, GO has a complicated nonstoichiometric atomic structure that is still not well understood in spite of of intensive studies involving many experimental techniques. Controversies often exist in experimental data interpretation. We report here a first principles study on binding energy of carbon 1s orbital in GO. The calculated results can be well used to interpret experimental X-ray photoelectron spectroscopy (XPS) data and provide a unified spectral assignment. Based on the first principles understanding of XPS, a GO structure model containing new oxidation species epoxy pair and epoxy-hydroxy pair is proposed. Our results demonstrate that first principles computational spectroscopy provides a powerful means to investigate GO structure.